Phenomenon Description

What is the difference between the impedance characteristics of the 2M interface boards D12B, D12S, and D75S.

Cause Analysis

The impedance characteristics of the 2M interface boards D12B, D12S, and D75S have the following differences:

The D12B interface board is compatible with 75-ohm and 120-ohm veneer boards, and can provide 75-ohm unbalanced interfaces and 120-ohm balanced interfaces, but does not have service protection.

The D12S interface board can only be compatible with 120 ohm veneer boards, and at the same time, it is a PDH interface inversion board with service protection function.

The D75S interface board is only compatible with 75 ohm veneer boards, and is also a PDH interface reversal board with service protection.

Note:

The processing board of D12B can be PQ1A (handling 75-ohmE1 ) and PQ1B (handling 120-ohmE1 ), but the actual application should be determined by the type of 2M header of the customer-side DDF rack to decide what kind of collocation to use, e.g., if the customer-side DDF rack is a 2M docking header with 75-ohm, then the interface board can be D12B or D75S, and the processing board is PQ1A.

The 75 ohm 2M header to the DDF shelf is coaxial cable, the 120 ohm 2M header is twisted pair (i.e., network cable), and the headers connected to the interface board all have the same DB44 connector.

Procedure

None

Recommendation Summary

None